A hydraulic powered circular saw is a popular tool used for such tasks as trimming tree limbs from around power lines and the like. A hydraulic powered motor is equipped with a saw blade and a long handle that enables the operator to reach a number of feet above his head when cutting tree limbs. The saw blade is powered by hydraulic fluid that is circulated under pressure through the motor.
Because it is important to electrically insulate the operator from the motor in the event that an electrical wire is contacted by the saw blade, the handle and hydraulic fluid lines are formed from nonconductive materials. Thus a rigid plastic sleeve forms the major length of the handle, e.g., 5 to 8 feet, and a pair of tubes having a center portion formed of plastic and the ends formed of metal, are contained inside the sleeve to provide the feed and return lines for the hydraulic fluid between the motor housing and the handle grip. A hydraulic fluid source is coupled to the ends of the tubes at the handle grip and the other ends of the tubes are inserted into the motor housing. Whereas the fluid is under pressure, leakage at the connections to the motor and fluid source are prevented by tight fitting O rings that are seated in the motor housing inlet and coupling.
The construction described above has been generally found to function very satisfactorily but only for a relatively short period of time. The whirling saw blade, and particularly during the cutting operation, sets up a vibration that passes through the motor housing and into the sleeve and tubes contained therein. The O rings at the ends of the tubes wear a groove in the metal ends of the tubes and as the fit and the O ring thus loosens, leakage results.
Heretofore the only way that this leakage could be effectively stopped was to replace the tubes. Simply cutting off the tip of the tube does not work because then the tube is too short for the length between the handle grip and motor housing as dictated by the rigid sleeve. Using a coupling sleeve type extension to add a new tip to this tube does not work because the added thickness prevents the tube from fitting inside the sleeve diameter. The tubes are an expensive component of the tool and their frequent replacement is costly to the tool's operation.